Method for decreasing the flammability of cellulosic fabrics

ABSTRACT

Cellulosic fabrics are rendered less flammable by reaction of acrylamidomethyl cellulose with sodium hypophosphite in the presence of ionizing radiation and then with bromine.

United States Patent 11 1 Walsh et al. a [451 Jan. 9, 1973 [54] METHOD FOR DECREASING THE [56] References Cited FLAMMABILITY OF CELLULOSIC UNITED STATES PATENTS FABRICS M 3,423,163 1 1969 t t l ..8 116.3 Inventors: William Kershlw Walsh; Henry 3,434,161 3/1969 I Ames Rutherford, both of Raleigh, 3,558,263 l/l97l Baitinger N.C. 3,300,273 l/l967 Kullman et a1. ..8/116.3 3,304,147 2/1967 Reinhardt et a1 ..8/116.3 Asslgnw Research Corponfiolh New York, 3,592,582 7/1971 Kullman et al. ..8/116.3 N.Y. 3,666,401 5/1972 Cahill et al. ..8/116.3 X

[22] Filed: NOV. 22, 1971 OTHER PUBLICATIONS PP N05 2011213 Walsh et al., Textile Research Journal, Vol. 35, pp.

52 us. Cl ..8/129, 8/116, 8/116 R, 'f' Emmi'fer-qemge Lesmes 8/1163, 8/120, 8/DlG. 18, 117/9331,

7 Attorney-Denms Clarke et a]. [51] Int. Cl ..D06m 13/40, @6111 15/36,

D06m 11/04 [57] ABSTRACT [58] Field of Senrch...8/l 16, 120, 116.3, 116 P, DIG. Cellulosic fabrics are rendered less flammable by reac- 18, 8/129 tion of acrylamidomethyl cellulose with sodium hypophosphite in the presence of ionizing radiation and then with bromine.

2 Claims, No Drawings METHOD FOR DECREASING THE FLAMMABILITY F CELLULOSIC FABRICS This invention relates to the modification of cotton or cellulosic textile fabrics. In one specific aspect, it relates to a method for decreasing the flammability of such fabrics and the modified fabrics thereby produced.

Cellulosic fabrics are widely used and the need for rendering such fabrics less flammable is very apparent. It is also known that the incorporation of phosphorous and/or halogen into fabrics decreases their flammability. However, prior art methods often result in other undesirable modifications of the fabric, such as making them stiff or harsh to the touch. We have discovered an improved approach to the incorporation of phosphorous and bromine into cellulosic fabrics wherein the soft hand of the fabric is not materially affected.

More specifically, the present invention is a method for decreasing the flammability of a cellulosic fabric which comprises reacting the fabric with an aqueous solution containing sodium hypophosphite in the presence of ionizing radiation and then with an aqueous solution containing bromine. The invention also contemplates the modified cellulosic fabric thereby produced.

In practicing the method of the present invention, the cellulosic fabric to be modified is treated with N- methylol acrylamide (NMA) in the presence of an acid catalyst according to the equation ll Cell-OH HOCHzNHC-CH=CH2 cellulose NMA ll Cell-OCHz--NHCCH=CH2 H2O acrylamidomethyl cellulose The procedure is described in more detail in US. Pat. No. 2,837,512 to Mantell.

The fabric reacted with NMA containing acrylamidomethyl cellulose is padded with an aqueous solution containing sodium hypophosphite at approximately neutral pH (hypophosphorous acid brought to pH 7 by addition of sodium hydroxide or like base) to pick up the desired amount of sodium hypophosphite, at least about percent by weight based on the dry fabric. Exposure of the padded fabric to ionizing radiation generates free radicals and causes the hypophosphite to react with and become affixed to the unsaturated portion of the acrylamidomethyl cellulose entity in the fabric. The most convenient source of ionizing radiation currently available is gamma radiation from radioactive isotopes of cobalt and from various uranium fission products. Irradiation is easily controlled and the extent of treatment will depend on the energy of the treating source. The amount of radiation employed should be sufficient to cause a major portion of the hypophosphite to become affixed to the fabric; excess radiation, which would tend to degrade the fabric, should be avoided. Satisfactory results are obtained using about 2 megarads of ionizing radiation generally at room temperature.

The resistance to burning of both cotton and rayon fabric were greatly improved by treatment with sodium hypophosphite. However, treatment with hypophosphite alone was not sufficient to completely inhibit combustion. It was found that reaction of residual double bonds in the phosphated acrylamidomethyl cellulose with bromine (aqueous bromine-bromide solution) made flame resistance virtually complete without adversely affecting the hand of the treated fabric. It was also found that the brominated fabrics had the added advantage of being somewhat anti-bacterial as determined by inhibition tests after incubation with nutrient media inoculated with staphylococcus. While this antibacterial effect diminished on repeated washing, it remained greater than that of untreated fabric.

Our invention is further described by means of the following illustrative examples:

1. Preparation of acrylamidomethyl cellulose Cotton fabric was padded with a solution containing 25 percent N-methylol acrylamide, 1 percent zinc nitrate, 1 percent hydroquinone and 0.1 percent surfactant to percent wet pickup, dried at 60 C., cured for 10 minutes at C. and then washed and dried. More conveniently, the fabric was padded with 25 percent NMA, 0.37 percent hydrochloric acid, and 0.1 percent surfactant, and then heated for 10 minutes at 70 C. without prior drying. The first method gave about a 12 percent increase in weight of cotton fabric and an 18 percent increase in weight of rayon treated. The second method gave about a 10 percent increase in weight for cotton and a 16 percent increase in weight for rayon.

2. Addition of sodium hypophosphite to acrylamidomethyl cellulose Acrylamidomethyl cellulose, cotton fabric with 11.1 percent weight gain from reaction with N-methylol acrylamide, was padded with an aqueous solution of sodium hypophosphite at pH 7. The padded fabric was dried, weighed, and irradiated with radioactive cobalt for 21 hours to a dose of 2.7 Mrads, washed and reweighed. The fabric containing 6.4 percent by weight of sodium hypophosphite after padding retained 5.1 percent of that salt after irradiation and washing.

Rayon fabric containing about 17 percent N- methylol acrylamide and cotton fabric containing 12% NMA were padded with 30 percent and 20 percent solutions of sodium hypophosphite, respectively. The padded fabrics were dried and irradiated 10 hours (1.3 Mrads), washed, dried and weighed. The rayon increased in weight by about 15 percent and the cotton by about 6 percent based on dry weight of material.

3. Addition of bromine to sodium hypophosphite containing acrylamidomethyl cellulose Cotton and rayon fabric treated according to the previous example were each immersed for 10 minutes in an aqueous solution containing 10 percent bromine and 15 percent potassium bromide. After rinsing and drying, additional weight gains of 3 percent and 7 percent for the rayon and cotton, respectively, were observed. The brominated fabrics had a soft hand.

When the brominated fabrics were subjected to the AATCC No. 344966 flammability test, the rayon showed zero afterflame and zero afterglow for both 12 and 2 second ignition times. The char lengths were 1.5

inches and less than 0.25 inches for the 12 second and 2 second ignition times, respectively. The cotton fabric, after twenty home launderings, had zero and 5 second afterflame times, zero afterglow, and 2.7 and 1.8 inch char lengths for the 12 second and 2 second ignition times. Untreated fabrics of the same type were virtually completely consumed in this test.

The process of the present invention is applicable to cellulose-containing fabrics generally. As used herein, the term fabrics" is meant to include textile fabrics of all kinds including woven and non-woven fabrics. The fabric may contain or be made from a natural cellulose material such as cotton or a regenerated cellulose material such as rayon.

Other variations in approach falling within the scope of the invention herein described will suggest themselves to those skilled in the art and our invention is as claimed.

We claim:

1. A method for decreasing the flammability of a cellulosic fabric which has been modified through reaction with an acidic solution of N-methylolacrylamide comprising reacting the fabric with an aqueous solution containing sodium hypophosphite in the presence of ionizing radiation and thereafter treating the fabric with an aqueous solution containing bromine.

2. A cellulosic fabric produced by the process of claim 1. 

2. A cellulosic fabric produced by the process of claim
 1. 